Heating pad



Jan. 2, 1940. MQCLEARY 2,185,692

HEATING PAD Filed June 19, 1939 2 Sheets-Sheet l ATTORNEYS Jan. 2,' 1940. N. H. MOCLEARY HEAT ING PAD Filed June 19, 1939 2 Sheets-Sheet 2 mmmm ATTORNEYS Patented. Jan. 1940 i UNITED STATES -nna'rnve ran 3 Nolen H. McClcary, Chicago, 111., assignor to Benjamin E. Lawrence, Chicago, Ill.

Application June 19, 1939, Serial No. 279,878

REISSUED 8 Claims. lol. 219-4 .My invention relates to heating pads.

Heat has long been used for the relief of pain. In modern practice, its therapeutic value has increased rather than decreased. The constant 6 improvement, for a score of years, or more, of the so-called electric heating pad has brought this device to the forefront'in the heat therapy field. It has achieved this position despite recognized imperfections which those in the industry have 10 sought to overcome.

A factor of considerable significance has been the control of heat. The usual practice has been to attach resistance wire, suitably covered, as with asbestos, to a supporting sheet-like member, such as suitably treated canvas, woven asbestos fabric or the like. Current control means are employed, conventionally secured to the same support as the resistance wire. Because of the necessity, in most cases, of providing for the control of the heat at several temperatures, and

the difliculties involved therein, several thermostatic elements are employed as a rule, sometimes with multiple wiring and with multiple leads thereto.

15 The effect of this practice, for a number of years more or less conventional, is the presence within the pad of considerable hard or unyielding inclusions which make contact with the body, particularly when the patient is lying on the pad 9 or holding it to a tender part, such as the face, either distasteful or painful. Those skilled in the art have sought for remedies for this con-' dition, such as decreasing the size of thermostats,-

changing the character of the wire, and the'like,

but principally in attempts to devise padding means which will not impair the delivery of heat to the outside. Requirements of the fire underwriters have been a limiting factor in development, and because of the character oi. the device,

6 :approval of the underwriters laboratories is important from the standpoint of both the manufacturer and user. v

One direction which development has taken is in the use of textile padding. This must be placed within or on the outsideof the imperiorate rubber envelope demanded by fire underwriters specifications. .No attempt in this direction has met with full success, because of the the '50 hazard introduced, the introduction of material which will fail because of the absorption of moisture, such as perspiration, the ineffectiveness of the material suppliedas a cushion,-or the loss of heat which results, At times, all of these dis-v advantages may be encountered.

' The principal object of my invention is to overcome the problems outlined hereinabove.

Another object is the provision of an improved heating pad.

A further object is the provision of a heating pad so adequately cushioned that a patient may lie on it with comfort, but which nevertheless will respond to deliver heat substantially to the extent as a generally similar pad not similarly cushioned.

In carrying out my invention, I employ material normally deemed of high heat insulating character, but so construct and employ such material that it has fully adequate cushioning action and only very slight heat insulating action.

I preferably employ the imperforate, relatively thin rubber envelope referred to hereinabove, and may employ suitably designed material of my invention either within or on the outside of this envelope. Mhximum cushioning effect is obtained with both. Within the rubber envelope, I employ, in a preferred embodiment, a layer of sponge rubber, provided with a series of openings insuiiicient in character and number to materially decrease the cushioning character of the sponge rubber, but sufiicient in total area to pass at least the major proportion of the heat generated by the heating element. Exteriorly of the rubber envelope, I preferably utilize an outside envelope Of textile material, having spaced sections of piling. Thepiling is 'substantially vertical to a supporting body of cloth, and, while it has more cushioning action as a heavy pad fabric, it has very little resistance to the flow of heat waves.

A preferred embodiment of the invention is shown in the accompanying drawings. Other objects and features of the invention will be deferred embodiment.

scribed in the detailed description of this pre- In the drawings,

Fig. 1 isv a perspective view'showing the complete heating pad;

Fig.2 is a plan view, with portions broken away to illustrate the relationship of the parts; Fig. 3 is an enlarged cross sectional view taken on the line 3-3 of Fig. 1;

Fig. 4 is a perspective view of the outer envelope;

Fig. 5 is a perspective view of the rubber enr Figs. 4 to 6, inclusive, which show the main parts of the complete pad. A heating element and heat control assembly I is sandwiched between layers ll of perforated aerated elastic material,

such as sponge rubber, and inserted in a rubber envelope l2. This rubber envelope is suitably but permanently closed, the cord conductor l3 extending through the closed edge. The rubber envelope and contents are inserted in the zipper-fastened outer envelope it, the resulting assembled product being shown in Fig. 1. The principal details of construction of the parts will be explained, and the reasons for and advantages of the construction used.

The member i0 may be conventional. It comprises a sheet-like support IE, to which resistance wire I1 is secured, as by stitching. The wire and support are properly selected so as to avoid burning. The wire may be suitably covered with asbestos, and the support may be either a suitable canvas fabric, or an asbestos fabric. Fig. 3 shows, in elevation, a thermostat i8, and any suitable number may be used, depending upon the design of the electrical circuit employed.

The layers ii are preferably sponge rubber,

with regularly arranged holes or perforations 19.

extending entirely therethrough.v Preferably, a layer i l is provided on both sides of the member Ill, so that either side of the pad may be placed against the body. In a standard size of pad, these layers are suitably one-quarter to threeeighths of an inch thick, and the total area of the holes is from one-third to one-half the total area of the layer. The design of the holes may vary, but round holes seem to be preferred to accomplish the object of the invention, namely, to combine full cushioning action and maximum heattransfer. '1

The rubber envelope I! may be a thin rubber without fabric backing, but a combination of a thin fabric and rubber is preferred. It may be secured, or adhesively secured, at the edges, depending upon the desire of the manufacturer and the type of rubber material used. Preferably, I employ a thin rubber-fabric material and close it by a double stitching operation. Because of the insulating character of the layers H, the rubber envelope i2 may, if desired, be dispensed with in favor of a simple type of fabric bag, but the advantages of the rubber-envelope are suillciently marked that I prefer to use it.

The outer envelope may be of plain weave, and formed as shown to permit ready. removal for laundering, the cushioning eflect of the layers Ii being adequate for all practical purposes. As shown, however, it includes a cloth base 2|, with sections 22- of piling spaced from each other.

This piling, as indicated, is attached to the cloth f base in such a manner that its individual threads are perpendicular to the cloth base. As a consequence of this construction, surprisingly enough, there is very little resistance to the passage of heat, the eflect being almost the same as.

if only the cloth base 2| were present. The piling, however, provides greater cushioning effect than would be provided by a heavily woven cloth of area:

may be left out of the combination, or it may be substituted by a textile envelope. The sponge rubber layers may be housed within the outside v envelope, and on the outside of the thin rubber envelope. The thin rubber sheeting comprising the envelope may be vulcanized onto the rubber layers, and the assembly then vulcanized at the three edges, or, alternatively, the holes i9 may extend only part way through the sponge rubber layer, leaving a thin, imperforate outer layer as theequivalent of the thin rubber envelope. i

I have explained my invention in detail in order that those skilled in the art may understand and practice it, but the claims are to be taken as definitive of its scope. i

What I claim as new and desire to protect by Letters Patent of the United States is:

1. In a heating pad, a sheet-like support for a heating element, a heating element, as a resistance wire, secured to said sheet-like support, a sponge rubber pad, on at least one side of said heating element, and an outer imperforate covering for said sheet-like support and pad, said sponge rubber pad provided with perforations sufllcient in total area to permit a substantial proportion of the heat from said heating element readily to pass therethrough, but insuflicient to permit breakdown-of the essential structure of said pad under pressure, whereby not 'to impair imperforate rubber bag member enclosing the heating element member and sponge rubber layers, said sponge rubber layers provided with a plurality of substantially regularly arranged perforations, the total area of all of said perforations comprising from one-third to one-half of the area of one surface through whichthey extend.

.3. In a heating pad, a sheet-like support member, resistance wire secured thereto to form a heating element, a thermostat secured to said support member and connected to said resistance wire to limit the temperature of said wire in responseto the passage of electric current therethrough, an imperforate rubber envelope enclosing the whole, and an outer envelope of textile material enclosing said rubber envelope, said textile material comprising a relatively thin cloth base, and a plurality of regularly arranged spaced sections of piling'substantially vertical to said cloth base. whereby said piling provides a cushioning action without limiting appreciably the passage of heat through the textile material as a whole.

4. In' a heating pad, a sheet-like support member, resistance wire secured thereto to form a heating element, a thermostat secured to said support member and connected to said resistance wire to limit the temperature of said wire in response to the passage of electric current therethrough, an imperforate rubber envelope enclosing the whole, and an outer envelope of textile material enclosing said rubber envelope, said textile material comprising a relatively thin cloth base. and a plurality of parallel spaced greases ridges of piling, the piling of said ridges composed of fibers disposed substantially vertical to the plane of said cloth, whereby said ridges of piling provide a cushioning action without limiting appreciably the passage of heat through the textile material as a whole.

5. The combination defined in claim 4, wherein said envelope of textile material is releasably closed along one edge thereof, whereby to permit ready removal thereof for laundering or exchange for a similar envelope. 1

6. The combination in a heating pad of the type employing an electric heating and control means, including electric resistance wires and thermostats secured to a sheet-like base, of a. pair of layers of aerated elastic rubber-like material havinc a plurality of perforations therein, the total area of which is from about'one-third to onehalf of the area of said layers, an imperiorate rubber envelope enclosing the same, and an outer envelope of textile material enclosing said rubber envelope, said textile material comprising a relatively thin cloth base, and a plurality of regularly arranged spaced sections of piling substanbase, whereby said piling provides a, cushioning action without limiting appreciably the passage or heat through the textile material as a whole.

8. In a heating pad, a sheet-like support member, resistance wire secured thereto, thermostatic control means associated with said wire to limit the delivery of electric current thereto in response to predetermined temperature, a layer of perforated sponge rubber on opposite sides of said total area' comprises from about one-third to one-=half of the total area of the layers, whereby not more than ten to fiiteen percent of the heat is absorbed by said layers, and the cushioning action thereof is substantially unimpaired.

NOLEN H. McChEARY. 

